I have some JavaScript that, I believe, is stuck in an infinite loop. I know I can just reload the page, but I have data in a form on the current page that I'd like to keep. The tab is completely unresponsive, so I can't just copy and paste everything and then reload. So is there any way to kill the javascript thread, but keep the DOM in Chrome?
You can open the developer console F12 and stop the script
Open chrome developer tools and go to the sources tab. On the right panel press "pause script execution".
looks like someone had the same problem
Cancel infinite loop execution in jsfiddle
Answer:
With the developer mode, go into resources and find your script and copy and paste it into a text document or a new window. If you can't find it in resources, do a search for a variable or line of code you used.
Related
How do I view all JS objects that I created in chrome? I know if I type window into the console, I will see everything, but where is the tab that is filled with all my things?
I think you might be looking for something like Chrome Breakpoints. Basically, in the developer tools, you will go to 'sources', click the file you are wanting to debug, and set a breakpoint on the line in the file that you want to see your active variables. You do this by simply clicking on the line number. When you reload, the browser will pause execution on this line and you will be able to see all the information you are looking for.
I have a problem when I am trying to check the source of an interesting page which keeps refreshing automatically every 3-5 seconds (presumably due to some js script) which resets my Inspect Element Inspector window every time the page is refreshed.
Is there any other way other to stop that page from refreshing or perhaps the Inspector window from resetting itself other than turning on NoScript to stop the page from refreshing automatically?
Usually I just open DevTools, switch to the appropriate panel if necessary, and hit pause.
Opening DevTools: Via menus, or by press F12, Ctrl+Shift+I, or Cmd+Shift+I depending on browser and OS.
Switching panels: Pick the panel from the tabs at the top of DevTools. It'll be called "Debugger" (Firefox, IE) or "Sources" (Chrome) or similar.
Pausing: In the Debugger/Sources panel, click the pause button (usually looks like the pause button on a television remote control, ||) or press the keyboard equivalent. Keyboard equivalents are
Firefox & Chrome: F8
IE: Ctrl+Shift+B
(Updated 2020-03-30)
In Firefox 74 this option is in Options -> Privacy & Security -> Permissions
(Original reply)
Firefox has the option to prevent refresh natively, the option is in Advanced->General->Warn me when websites try to redirect or reload the page
The most popular solution for this problem is to trap the beforeunload event. The browser will ask the user for confirmation to leave the page. The code, in its simplest form, looks like this:
window.onbeforeunload = function() { return true }
You can enter this code in console. Alternately, you can simply paste the following URL in the browser address bar (console not required). You can even bookmark it.
javascript:window.onbeforeunload = function() { return true }
Be advised that modern browsers might chop off the javascript: part when you paste it inside the address bar; make sure you type it back.
To determine the cause of redirect in Firefox, try the following:
Open Web Developer Tools (CTRL + SHIFT + I), open "Toolbox Options" and check the "Enable persistent logs" option. This makes the logs persist across page loads (logs are cleared otherwise).
Now switch to "Network Monitor" tab.
Open the URL and let it refresh.
Inside the Network Monitor > Cause column you will find out why the page reloads.
The cause column is pretty ambiguous (Chrome does a much better job). However, if JavaScript was used to trigger page (re)load then it at least shows you the filename and line number of that script.
When the page is still loading, you can press the Esc key. While the page is still white, press it. When you stop the page from loading at this point, this usually stops all the auto loaded javascript. Any scripts that run on actions are usually not effected. Each page is different, try different timings.
When I use a site called NovelUpdates there is javascript that can make certain elements hidden, and when I press Esc on page load all the elements that would be hidden after page load are visible. Then when I click a button that would execute javascript that operates with no problems. NoScript isn't going to solve your issue I believe.
Another example of this are those websites with annoying boxes that pop out after 10 seconds that says you aren't a member and can't view any more of this site without logging in, like some news article websites.
What you could do is use the command exit(), which is the equivalent to die in php and simply stops the script.
If you don't know what's causing it and you don't want to look for the "bad boy", then you might as well stop the entire script at the very bottom of the page.
Is there anyway to prevent changes to web pages such as a live chat or a video feed? Im guessing its a javascript that times out the webpage and then exits it or prevents further entry.
I saw this question: Freeze screen in chrome debugger / DevTools panel for popover inspection?
What I did was I inspected the element, then went to the line of code and then clicked on :hover but the script still executed and locked me out. Any other ways you can think of to prevent changes being made to a page?
Chrome allows you to disable JavaScript on certain pages, to do so click on the globe of the URL bar and it will show some permission options for the site you are. There disable JavaScript.
How to deliberately freeze javascript in chrome (plugin/console)
Found another solution in the link above:
Open Chrome javascript console
Go to "sources"
On the right side, click the little "pause" icon, or press F8 to pause script execution.
I'm running this javascript to click a link through my Chrome browser
document.getElementById('extractResults').click();
It's clicking fine, until I navigate away from the browser tab or window. Any insights into how to execute the action even after I've navigated away from the tab?
Thanks!
I guess it depends on how you're "running this javascript"... are you using setInterval() or something similar?
You might do a google search for "javascript background tabs" -- there are a lot of related issues (such as this and this) and the bottom line seems to be that modern browsers are saving CPU (etc) by not running everything when in the background.
I'm looking at a web page where when I push the submit button on a form, it brings up a new page where it runs some javascript and then closes the window.
Is there any way I can step through the javascript on the new page? I tried setting break on next in Firebug on the first page, but the next page still closes the window.
(I'm open to other tools besides Firebug if neccessary, I just need to step through the javascript)
Update:
I should have mentioned I don't have access to the code :-(
If you have access to the code, you can place this little statement where you want to have a breakpoint:
debugger;
I am not sure about firebug, but I expect it to work there too.
put debugger; in your JavaScript code. and press F12 key just after window open.